Michael Sullivan was a character in Tom Paris' holodeck program called Fair Haven. He owned the local pub in the village of Fair Haven which was set in 19th century Ireland.
Captain Kathryn Janeway visited his pub and became interested in him. Over time, she made several adjustments to his character to better suit her romantically. Eventually, she ordered the computer to prevent her from being able to make any more adjustments to the character. (VOY episode: "Fair Haven")
In early 2378 after returning to Earth, Janeway ordered the crew of Voyager to delete any holodeck programs they regarded as "personal". Janeway herself went on one last visit to Fair Haven in order to tell Michael Sullivan that she had made it home and that she would not return to Fair Haven. (VOY novel: Homecoming)
Candace Roske was among the crew assigned to work aboard Voyager while Project Full Circle got as much information and technology from the ship as possible. She often used the crew's holodeck programs and her uses included visiting Fair Haven. Roske really enjoyed her trip, though she thought that the bartender - Sullivan - was "a bit mopey." (VOY novel: The Farther Shore)
Connections[]
Michael Sullivan article at Memory Alpha, the wiki for canon Star Trek.